The present invention relates to a projection-capacitive touch panel which is capable of detecting multi-points of fingertip.
Recently, in electronic device such as a mobile phone, a smart device (for example, a tablet device, an electronic book reader and so on), a car navigation system and so on, a display device (display device with touch panel: touch panel device) including a touch panel function which has effects intuitive operation and excellent durability is mounted as one form of interface.
The touch panel is a position input system so as to detect a touch from an indicator such as a finger or stylus and so as to identify a position coordinate of the touch. The detection method is divided broadly into a resistive film system including an analog resistive film type and a matrix resistive film type, a capacitance system including a surface capacitance type and a projection-capacitive type, an optical system including an infrared scanning type and a retroreflective type, and an ultrasonic system including a surface acoustic wave type and a plate wave type. Various types are put to practical use.
In recent years, especially the demand for the projection-capacitive type touch panel in the above mentioned detection method is expanded. The projection-capacitive type touch panel detects the capacitive change of an electrode near a fingertip as a position coordinate on the touch panel from two vertical and horizontal electrode rows when the fingertip approaches.
Patent Literature 1 described below discloses a capacitive type touch panel. The touch panel has a plurality of detection electrodes for detecting that a conductive body approaches a front surface of the substrate, and a wiring electrode for transmitting a detection signal to an external circuit. The wiring electrode is electrically connected to the detection electrode. Further, the plurality of the detection electrodes has a detection area formed on a central portion of the substrate. The wiring electrode connected to the detection electrodes has a wiring area formed by being collected in an outer side of the detection area.
Meanwhile, in a capacitance coupling type touch panel, when a conductor approaches the detection electrode, a capacitance formed between the conductor and the detection electrode is changed, weak current flowing in the changed capacitance is detected, and thereby a conductor position is identified.
However, when noise current caused by external discharge such as static electricity is input to the detection electrode and the wiring electrode around the upper surface of the substrate other than the detection area and the end portion thereof, there is a problem that false recognition of the position coordinates occurs and the electrode itself are destroyed.
For this reason, in the touch panel of the Patent Literature 1, a first shielding electrode is formed so as to surround an area including the detection area and the wiring area, and noise entering from the end portion of the substrate is shielded. Thereby, the touch panel prevents noise from reaching the wiring electrode and the detection electrode.
Patent Literature 1: JP 2010-218542 A